<template>
    <div>
        <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
            <span class="iconfont header-abs-back">&#xe624;</span>
        </router-link>
        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            <router-link to='/'>
                <span class="iconfont header-fixed-back" >&#xe624;</span>
            </router-link>
            景点详情
        </div>
    </div>
</template>

<script>
    export default {
        name: 'DetailHeader',
        data(){
            return{
                showAbs: true,
                  opacityStyle: {
                    opacity: 0
                }
            }
        },
        methods:{
            handleScroll(){
                const top = document.documentElement.scrollTop
                if(top > 60){
                    let opacity = top/140
                    opacity = opacity > 1 ? 1:opacity
                    this.opacityStyle = { opacity }
                    this.showAbs = false
                }
                else{
                    this.showAbs = true
                }
            }
        },
        activated () {
            window.addEventListener('scroll', this.handleScroll)
        },
        deactivated () {//移出界面就会触发
            window.removeEventListener('scroll', this.handleScroll)
        }
    }
</script>

<style lang="stylus" scoped>
    .header-abs
        position: absolute
        left: .2rem
        top: .2rem
        width: .8rem
        height: .8rem
        line-height: .8rem
        border-radius: .4rem
        text-align: center
        background: rgba(0, 0, 0, .8)
        .header-abs-back
            color: #fff
            font-size: .4rem
    .header-fixed
        z-index: 2
        position: fixed
        top: 0
        left: 0
        right: 0
        height: .64rem
        line-height: .64rem
        text-align: center
        color: #fff
        background: #00bcd4
        font-size: .32rem
        .header-fixed-back
            position: absolute
            top: 0
            left: 0
            width: .64rem
            text-align: center
            font-size: .4rem
            color: #fff
</style>